Process and device for replacing an underground pipe

Abstract

In order to replace a first underground pipe such as a metal pipe by a second pipe of mean diameter substantially equal to or greater than that of the first pipe, the first pipe is cut longitudinally by a localized projection of a flow of matter, particles or radiation thanks to a localized projection means which are displaced inside the first pipe in order to divide the first pipe longitudinally into at least two segments. Cutting by localized projection avoids in particular the creation of vibrations during fragmentation of the pipe to be replaced.

What is claimed is: 
     
       1. A process for replacing a first underground pipe with a second pipe whose mean diameter is substantially equal to that of said first pipe, comprising the steps of: providing cutting means for displacement inside the first pipe, said cutting means including localized projection means for localized projection of a flow of matter; and   cutting said first pipe over at least a part of its thickness, using the localized projection of the flow of matter onto said first pipe, with the localized projection means which are displaced inside the first pipe, in order to longitudinally divide said first pipe into at least two cut segments.   
     
     
       2. The process of claim 1, further comprising the step of: spreading apart said cut segments of said first pipe with spreader means which are displaced inside the first pipe in order to allow an introduction of said second pipe which is intended to replace said first pipe.   
     
     
       3. The process of claim 2, wherein the cut segments of the first pipe are spread apart immediately after cutting by the localized projection, and by making the projection means and the spreader means advance simultaneously with each other inside the first pipe. 
     
     
       4. The process of claim 2, wherein cutting of the first pipe by the localized projection is effected in the course of a first period of time during which the localized projection means are made to advance inside the first pipe, and the cut segments of said first pipe are spread apart during a subsequent period of time for positioning the second pipe, the cut segments being spread apart with the aid of said spreader means introduced separately in the first pipe after said localized projection means and advancing inside the cut first pipe independently of said localized projection means. 
     
     
       5. The process of claim 2, wherein a protection sleeve having a head which is towed behind said spreader means is inserted into said cut and spread apart first pipe and then said said pipe is introduced inside said sleeve to be placed in position. 
     
     
       6. The process of claim 2, wherein said second pipe has a head which is towed behind said spreader means and is inserted directly into said cut and spread apart first pipe to be placed in position. 
     
     
       7. The process of claim 1, wherein the localized projection which cuts said first pipe is produced by a directional jet of water under pressure. 
     
     
       8. The process of claim 1, wherein the localized projection which cuts said first pipe is produced by a directional jet constituted by a mixture of water and of abrasive particles under pressure. 
     
     
       9. The process of claim 1, wherein the localized projection which cuts said first pipe is produced by a flow of gaseous oxygen and a flow of gaseous fuel burned with the oxygen by said cutting means. 
     
     
       10. The process of claim 9, wherein the gaseous fuel is acetylene. 
     
     
       11. The process of claim 1, wherein the localized projection which cuts said pipe is produced by a flow of gaseous matter and a flow of electrons supplied by plasma arc means forming said cutting means. 
     
     
       12. The process of claim 1, wherein the localized projection which cuts said first pipe is produced by a radiation of coherent light supplied by laser beam means forming said cutting means. 
     
     
       13. The process of claim 1, wherein the localized projection which cuts said first pipe is produced by fusion drilling means forming said cutting means. 
     
     
       14. The process of claim 1, wherein the localized projection which cuts said first pipe is produced by a flow of gaseous matter and of particles supplied by powdered iron torch means forming said cutting means. 
     
     
       15. The process of claim 1, wherein the localized projection on the first pipe is produced so as to cut only through a part of thickness of the first pipe, so as to maintain between the cut segments of the first pipe connecting elements of small thickness which may be easily broken during the subsequent passage of a spreader means inside said pipe. 
     
     
       16. The process of claim 1, wherein the localized projection onto the first pipe is produced so as to cut the thickness of the first pipe. 
     
     
       17. The process of claim 15, wherein the thickness of the pipe to be cut is measured by measuring means which cooperate with adjusting means for automatically adjusting a depth of the cut.